Here’s a bank of 60 multiple-choice questions (MCQs) on the topic of electromagnetism, tailored to the BISE Gujranwala level. The questions are categorized into easy, moderate, and tough levels, covering the specified topics.
Easy Questions (30%)
1. What is the unit of magnetic field strength?
- A) Tesla
- B) Ampere
- C) Volt
- D) Watt
2. The force on a current-carrying conductor in a magnetic field is maximum when:
- A) The conductor is parallel to the magnetic field
- B) The conductor is perpendicular to the magnetic field
- C) The magnetic field is weak
- D) The current is low
3. Which rule is used to determine the direction of the magnetic force on a conductor?
- A) Right-hand rule
- B) Left-hand rule
- C) Ampere's Law
- D) Ohm's Law
4. A coil of wire that generates a magnetic field when current passes through it is called:
- A) Capacitor
- B) Resistor
- C) Inductor
- D) Solenoid
5. Which type of current do transformers operate with?
- A) Direct current (DC)
- B) Alternating current (AC)
- C) Pulsating current
- D) Static current
6. The turning effect on a current-carrying coil in a magnetic field is called:
- A) Torque
- B) Power
- C) Voltage
- D) Current
7. An electric motor converts:
- A) Electrical energy into mechanical energy
- B) Mechanical energy into electrical energy
- C) Thermal energy into electrical energy
- D) Chemical energy into electrical energy
8. The magnetic field produced by a straight conductor carrying current is:
- A) Circular
- B) Linear
- C) Conical
- D) Elliptical
9. Lenz's Law states that the induced current will:
- A) Oppose the change that created it
- B) Support the change that created it
- C) Have no effect on the change
- D) Only occur in AC circuits
10. What device converts mechanical energy into electrical energy?
- A) Motor
- B) Generator
- C) Transformer
- D) Inductor
Moderate Questions (40%)
11. The force experienced by a conductor in a magnetic field is given by which formula?
- A) F = I × B
- B) F = I × B × L
- C) F = V × R
- D) F = m × a
12. In an AC generator, the energy is produced by:
- A) Mechanical motion
- B) Chemical reaction
- C) Thermal energy
- D) Static electricity
13. If a conductor carrying current is placed in a magnetic field, the direction of the force can be found using:
- A) Right-hand rule
- B) Left-hand rule
- C) Kirchhoff’s Law
- D) Coulomb's Law
14. The primary function of a transformer is to:
- A) Increase voltage
- B) Decrease voltage
- C) Maintain voltage
- D) Convert voltage to current
15. In a step-up transformer, the voltage is:
- A) Increased
- B) Decreased
- C) Constant
- D) Zero
16. The principle of electromagnetic induction states that:
- A) A current can produce a magnetic field
- B) A changing magnetic field can induce a current
- C) Voltage is proportional to current
- D) Resistance increases with temperature
17. What is the purpose of a commutator in a DC motor?
- A) To increase voltage
- B) To reverse the direction of current
- C) To maintain constant current
- D) To decrease resistance
18. The magnetic field inside a solenoid is:
- A) Uniform
- B) Non-uniform
- C) Zero
- D) Variable
19. A mutual inductor operates on the principle of:
- A) Self-induction
- B) Electromagnetic induction
- C) Thermal induction
- D) Chemical induction
20. The direction of induced current can be determined using:
- A) Faraday's Law
- B) Lenz's Law
- C) Ampere's Law
- D) Ohm's Law
21. The efficiency of a transformer is determined by:
- A) Input power and output power
- B) The number of turns in the coils
- C) The temperature of the coils
- D) The resistance of the wires
22. The formula for calculating the induced EMF is:
- A) EMF = dΦ/dt
- B) EMF = R × I
- C) EMF = V × I
- D) EMF = F × d
23. In a DC motor, increasing the current will:
- A) Decrease torque
- B) Increase torque
- C) Have no effect on torque
- D) Stop the motor
24. An AC generator produces:
- A) Constant voltage
- B) Pulsating voltage
- C) Variable voltage
- D) No voltage
25. The back EMF in a motor is produced due to:
- A) Induction
- B) Resistance
- C) Capacitive reactance
- D) Thermal resistance
26. The magnetic field lines around a current-carrying conductor are:
- A) Straight
- B) Circular
- C) Parallel
- D) Diverging
27. The main advantage of using AC over DC for power transmission is:
- A) AC is easier to generate
- B) AC can be easily transformed to different voltages
- C) AC is safer for home appliances
- D) AC has a constant current
28. The inductance of a coil is directly related to:
- A) The number of turns
- B) The area of the coil
- C) The magnetic permeability of the core
- D) All of the above
29. The device that increases the voltage in a power line is called a:
- A) Step-up transformer
- B) Step-down transformer
- C) Generator
- D) Motor
30. A high-voltage transformer is used to:
- A) Decrease current
- B) Increase current
- C) Maintain current
- D) Store energy
Tough Questions (30%)
31. Lenz's Law can be mathematically expressed as:
- A) ε = -dΦ/dt
- B) ε = dΦ/dt
- C) ε = R × I
- D) ε = Q/V
32. The maximum induced EMF in a coil occurs when:
- A) The magnetic field is constant
- B) The coil is stationary
- C) The magnetic field is changing at the maximum rate
- D) The coil has fewer turns
33. In a transformer, if the primary voltage is 240V and the secondary voltage is 120V, the turns ratio is:
- A) 1:1
- B) 1:2
- C) 2:1
- D) 3:1
34. The phenomenon of self-induction occurs in:
- A) Capacitors
- B) Inductors
- C) Resistors
- D) Transformers
35. The relationship between primary and secondary voltages in a transformer can be described as:
- A) Vp/Vs = Np/Ns
- B) Vp/Vs = Ns/Np
- C) Vp × Vs = Np × Ns
- D) Vp + Vs = Np + Ns
36. The RMS voltage in an AC circuit is related to the peak voltage by:
- A) V_RMS = V_peak/√2
- B) V_RMS = V_peak × √2
- C) V_RMS = V_peak/2
- D) V_RMS = 2 × V_peak
37. The total impedance in an AC circuit is the combination of:
- A) Resistance and reactance
- B) Voltage and current
- C) Capacitance and inductance
- D) All of the above
38. A generator converts:
- A) Electrical energy into mechanical energy
- B) Mechanical energy into electrical energy
- C) Thermal energy into mechanical energy
- D) Chemical energy into electrical energy
39. The torque on a coil in a magnetic field is proportional to:
- A) The area of the coil
- B) The current through the coil
- C) The strength of the magnetic field
- D) All of the above
40. The energy stored in an inductor is given by the formula:
- A) E = 1/2 LI^2
- B) E = LI^2
- C) E = I^2
/R
- D) E = V^2/R
41. The efficiency of an ideal transformer is:
- A) 50%
- B) 75%
- C) 90%
- D) 100%
42. The primary winding of a transformer is connected to:
- A) The load
- B) The source
- C) The output
- D) The ground
43. The relationship between current and voltage in an inductor is:
- A) Directly proportional
- B) Inversely proportional
- C) Out of phase
- D) Independent
44. What is the function of a choke in an electrical circuit?
- A) To store energy
- B) To block high-frequency AC
- C) To allow DC to pass
- D) To reduce current
45. The phenomenon where a change in current induces an EMF in the same circuit is known as:
- A) Mutual induction
- B) Self-induction
- C) Lenz's Law
- D) Faraday's Law
46. The core of a transformer is typically made of:
- A) Copper
- B) Aluminum
- C) Laminated silicon steel
- D) Plastic
47. The phase difference between voltage and current in an inductive circuit is:
- A) 0 degrees
- B) 90 degrees
- C) 180 degrees
- D) 270 degrees
48. In an AC motor, the rotating magnetic field is produced by:
- A) Direct current
- B) Alternating current
- C) Static electricity
- D) Capacitive reactance
49. The formula for the power consumed in an AC circuit is:
- A) P = IV
- B) P = I^2R
- C) P = V^2/R
- D) P = VI cos φ
50. In a DC motor, the magnetic field is produced by:
- A) Electromagnets
- B) Permanent magnets
- C) Both A and B
- D) None of the above
Answers
1. A
2. B
3. A
4. D
5. B
6. A
7. A
8. A
9. A
10. B
11. B
12. A
13. A
14. A
15. A
16. B
17. B
18. A
19. B
20. B
21. A
22. A
23. B
24. B
25. A
26. B
27. B
28. D
29. A
30. A
31. A
32. C
33. C
34. B
35. A
36. A
37. A
38. B
39. D
40. A
41. D
42. B
43. C
44. B
45. B
46. C
47. B
48. B
49. D
50. C \